This invention relates to a fluid dispensing apparatus and method, and more particularly to an apparatus and method for sniffing, that is, retracting residual fluid of dispensing back into a dispensing outlet.
A major problem in the dispensing of fluid materials, particularly non-gaseous flowable liquids of various viscosities, including even those approaching a pasty character, is that of avoiding the mess caused by drips from the dispensing outlet or nozzle. The problem is not alone confined to the mess caused by drips and the uncertainty of their occurrence. In many cases accurate proportioning of a dispensed quantity can be upset by extra drips or the failure of a drip to occur when the proportioning measurements call for that extra drip. This problem is particularly acute in the mixing and tinting of paints, especially where only a very small quantity of colorant material is to be added to a particular base material. The problem is, however, not limited to paint tinting and occurs whenever dispensing is to be accomplished with precision and without mess.
The problem is one of long standing. Illustratively, U.S. Pat. No. 2,103,817 issued Dec. 28, 1937 to B. E. Johnson provides a complex solution involving a multitude of arms and cams to create a suction effect for withdrawing residual dispensed fluid so as to avoid drips or stringing of material and causing a mess. U.S. Pat. No. 2,107,987 issued Feb. 8, 1938 to B. E. Johnson continues the approach of employing a multitude of arms and cams. A still further approach for solution to the problem is set forth in U.S. Pat. No. 2,413,916 issued Jan. 7, 1947 to M. Hallead, where the approach taken is to plug the dispensing outlet and also employ suction.
All known approaches for solution to the problem have presented the art with either a complex system of apparatus elements or with specially designed components which add substantial cost to the dispensing apparatus, particularly as compared to the solution provided by this invention.
The solution of this invention is particularly noteworthy when it is recognized that the basic dispensing apparatus illustrated in the drawings has been known for years as an entity apart from its combination with the special features forming the sniff device and the method of its operation according to this invention.